High-speed scanner having image processing for improving the color reproduction and visual apperance therof

ABSTRACT

A scanner for digitizing a document includes a digitizer for digitizing the document into a first color space; a circuit for converting the digitized data into a second color space having a luminance channel and two chrominance channels; a multiplexer having text, approximate actual color of a uniform area and a predetermined color as input for selecting either the text, approximate actual color or the predetermined color as outputs; and multiplexer control input which determines which of the outputs will be selected as actual output based on a uniform area of the document.

FIELD OF THE INVENTION

[0001] The invention relates generally to the field of high-speed,document scanners, and more particularly, to a method and apparatus forimproving the color reproduction and visual appearance of the scanneddocuments.

BACKGROUND OF THE INVENTION

[0002] High-speed, document scanners are used to scan documents into adigital file for efficient storage of the documents, typicallycommercial-type documents, for later retrieval. These scanners typicallyincludes a plurality of mechanical and electromechanical components forpassing the document therethrough during the scanning process, as iswell-known in the art. Such apparatuses, however, can cause undesiredartifacts in the digital file representing the scanned document due tobending of the documents during processing, undesirable light reflectionangles and the like. To reduce these artifacts, such high-speed scannerstypically include standard image processing which processes the digitalfile for producing higher quality digital files.

[0003] Although the present method and apparatus for scanning documentsis satisfactory, they include drawbacks. The standard image processing,color correction produces lines and/or text which are lighter thandesired and a background which is aesthetically unpleasing and/or aninaccurate representation thereof. Therefore, a need exists for improvedimage processing in high-speed scanners which reduce or eliminate theseundesirable artifacts

SUMMARY OF THE INVENTION

[0004] The present invention is directed to overcoming one or more ofthe problems set forth above. Briefly summarized, according to oneaspect of the present invention, the invention resides in a scanner fordigitizing a document comprising: (a) a digitizer for digitizing thedocument into a first color space; (b) a color space converter forconverting the digitized data into a second color space having aluminance channel and two chrominance channels; (c) a multiplexer havingtext, approximate actual color of uniform area and a predetermined coloras input for selecting either the text, approximate actual color or thepredetermined color as outputs; and (d) multiplexer control input whichdetermines which of the outputs will be selected as actual output basedon a uniform area of the document.

[0005] It is an object of the present invention to provide a high-speedscanner that produces high-quality text and uniform areas having theactual color of the document, either white or some chromatic color.

[0006] It is a feature of the present invention to include a multiplexerthat will output, either output-high-quality text or the actual color ofthe uniform area depending on the input from two control signals.

[0007] It is an advantage of the present invention to provide imageprocessing for producing high-quality text and accurate colorreproduction of uniform areas with a combination of compact integratedcircuits.

[0008] These and other aspects, objects, features and advantages of thepresent invention will be more clearly understood and appreciated from areview of the following detailed description of the preferredembodiments and appended claims, and by reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic diagram of the improved image processing ofthe present invention; and

[0010]FIG. 2 is a detailed block diagram of an object dilation of FIG.1.

DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following description, the present invention will bedescribed in the preferred embodiment in hardware implementation, moreparticularly integrated circuits. However, those skilled in the art willreadily recognize that the equivalent of such hardware may also beconstructed in software.

[0012] Referring to FIG. 1, the present invention includes a high-speedscanner 10 having a digitizing device 20 for digitizing documents 30scanned therethrough. The digital file representation of the scanneddocument 30 includes a plurality of digital color channels, typicallyred, green, and blue, representing the scanned document. The colorchannels are passed through a color conversion lookup table 40 forconverting the red, green and blue signals into a color space having aluminance channel and two chrominance channels. In the preferredembodiment, the chrominance channels are preferably Cb and Cr. Thesecolor and luminance channels are then passed through a standard,color-correction lookup table 50 for processing the digital file throughstandard image processing algorithms. Such standard image processingalgorithms are those as are in the prior art and will not be discussedin detail herein. These algorithms correct for, for example, thespectral sensitivity of the imaging sensor and light source, whichresults in enhancing the chrominance information and reducing thecontrast of the luminance channel.

[0013] The chrominance channels after color correction and the luminancechannel before color correction are then passed as one of three inputsto a multiplexer 60. This signal represents the lines and/or text of thedocument 30. The luminance channel before color correction is alsopassed to a line and text extractor 70 that produces a bi-tonal orbinary signal for extracting any line and/or text in the document 30.This line/text extractor 70 is well-known in the art, such as thatdescribed in U.S. Pat. No. 5,583,659, and will not be discussed indetail herein. The bi-tonal signals is then dialated by a 3×3 dilationintegrated circuit 80 to expand the width of the characters clipped bythresholding during the line/text extraction process. Referring brieflyto FIG. 2, assuming that the black pixel (indicating lines and/or text)is indicated with “1” and the white pixel (indicating uniform areas) isindicated with “0” in a binary image, the image dilation is to expandthe region of black dots by a local neighborhood. The center pixel “o”at the output is set to “0” only when all neighboring pixels X1 in a 3×3window, where I=1, 2, . . . 8, are matched with the 3×3 zero mask.Otherwise, the center pixel “o” “a” the output is indicated with a blackpixel, “1.” The output of the dilation is a signal having two codevalues; one code value representing the text, typically the code value1, and the other code value representing the background, typically thecode value zero. The signals then passed to the multiplexer as one oftwo control signals.

[0014] Referring back to FIG. 1, the luminance and two chrominancechannels all after color correction are passed as another input to themultiplexer 60. This signal produces a signal representative of theactual color of uniform areas, which areas are typically of backgroundareas.

[0015] As for the other control input, the chrominance channels and theluminance channel all after color correction are then passed to aneutral/color separation integrated circuit 100 for deciding whether theuniform area is white (neutral) or some chromatic color. A pixel isclassified as neutral if |C₁−128|<C_(th) and |C₂−128|<C_(th), else it isclassified as color. Where the C₁ and C₂ are the two chromaticity valuesat the pixel of interest. The value “128” is the perfect neutral value.The C_(th) is a threshold value for tolerance of noise variation incolor capture. This signal is also passed as a control signal to themultiplexer 60.

[0016] The third input to the multiplexer 60 is of a predeterminedcolor, preferably neutral in the present invention, which includes aluminance value of 255 and chrominance values of 128 and stored inmemory 110. This signal is representative of a white background.

[0017] The operation of the multiplexer is as follows. First, thedilated signal from the 3×3 dilation 80 determines whether themultiplexer 60 will choose either text or a uniform area (eventuallychoosing either the approximate actual color of the uniform area orwhite, as described below, if the uniform area is chosen) as the output.If text is chosen, obviously the multiplexer 60 will output the textcode values as the output for this particular pixel location. If theuniform area is chosen for this particular pixel location, the signalfrom the neutral/color separator integrated circuit 100 will determinewhether white code vales, or the code values representative of theactual color the uniform area is chosen for this pixel location, asdescribed hereinabove.

[0018] The multiplexer 60 then passes its output signal to any suitablestorage media (not shown), such as electronic memory and the like. Themedia stores the entire digital representation of the document from themultiplexer along with any associative information suitable for queryduring retrieval. During query, the user will query a computer systemhaving a plurality of digital representations of documents forretrieving the corresponding digital representation of the documentassociated with the query.

[0019] The invention has been described with reference to a preferredembodiment. However, it will be appreciated that variations andmodifications can be effected by a person of ordinary skill in the artwithout departing from the scope of the invention.

PARTS LIST

[0020]10 High-speed scanner

[0021]20 Digitizing device

[0022]30 Digitizing document

[0023]40 Color conversion lookup table

[0024]50 Color-correction lookup table

[0025]60 Multiplexer

[0026]70 Line/text extractor

[0027]80 Dilation integrated circuit

[0028]100 Neutral/color separation integrated circuit

[0029]110 Memory

What is claimed is:
 1. A scanner for digitizing a document comprising:(a) a digitizer for digitizing the document into a first color space;(b) a color space converter for converting the digitized data into asecond color space having a luminance channel and two chrominancechannels; (c) a multiplexer having text, approximate actual color of auniform area and a predetermined color as input for selecting either thetext, approximate actual color or the predetermined color as outputs;and (d) multiplexer control input which determines which of the outputswill be selected as actual output based on a uniform area of thedocument.
 2. The scanner as in claim 1, wherein the multiplexer controlinput includes a first logic input for determining whether a pixel istext or a uniform area, and a second logic input for determining whetherthe uniform area is to be the approximate actual color or thepredetermined color.
 3. The scanner as in claim 1, wherein thepredetermined color is white.
 4. The scanner as in claim 2, wherein thesecond logic input includes a line and/or text extractor circuit fordetermining whether a uniform or non-uniform area exist.
 5. The scanneras in claim 4, wherein the second logic input further includes adilation circuit for enlarging the extracted line and/or text.
 6. Thescanner as in claim 3, wherein the first logic input includes athreshold circuit for determining whether the uniform area is white orchromatic color.
 7. A method for scanning and digitizing documents, themethod comprising the steps of: (a) digitizing the document into a firstcolor space; (b) converting the digitized data into a second color spacehaving a luminance channel and two chrominance channels; (c) providingtext, approximate actual color of uniform area and a predetermined coloras multiplexed input, and providing multiplexed output as either thetext, approximate actual color or the predetermined color as outputs;and (d) determining which of the outputs will be selected as actualoutput based on a uniform area of the document.
 8. The method as inclaim 7, wherein step (c) includes (e) determining whether a pixel istext or a uniform area, and (f) if the uniform area, determining whetherthe uniform area is to be the approximate actual color or thepredetermined color.
 9. The method as in claim 7, wherein step (c)includes providing white as the predetermined color.
 10. The method asin claim 8, wherein step (e) includes (g) providing a line and/or textextractor circuit for determining whether a uniform or non-uniform areaexist.
 11. The method as in claim 10, wherein step (g) includes furtherproviding a dilation circuit for enlarging the extracted line and/ortext.
 12. The method as in claim 8, wherein step (e) includes providinga threshold circuit for determining whether the uniform area is white orchromatic color.